In the case of stenosis in the carotid artery, atherosclerotic plaques are present at the vessel wall of the external carotid artery, the internal carotid artery, or the common carotid artery. These plaques have to be removed as they hinder the blood flow. A number of catheter-based angioplasty procedures as well as various surgical and non-surgical procedures have been developed for this reason. There is, however, a risk with these procedures, whereby parts of the plaque or other material may loosen and be released as emboli into the blood stream. In particular, such released particles can migrate in the direction toward the cerebral blood vessels due to the antegrade (i.e., forward moving) blood flow. The emboli have a high probability of becoming lodged within the cerebrovasculature causing flow blockage, brain tissue ischemia, and cell death. This represents a major risk for the patient. Vessel filters, which are supposed to block micro and macro-sized particles, have been developed in order to minimize or avoid these risks.
Conventional filter devices are disadvantageous in that they have to be positioned in a distal position relative to the stenosis in order to catch the released or sloughed off particles, which, according to the natural antegrade blood flow, would be transported towards the cerebral brain tissues and ultimately the brain. These vessel filters thus have to be guided beyond the stenosis before they can be deployed. Unfortunately, the process of guiding the filter through the area of the stenosis may itself result in the dislodging of particulate matter, which then may lead to emboli.
A so-called proximal protection system has been suggested as an additional protection against such risks. This system uses the selective placement of two inflatable balloons to effect retrograde blood flow (i.e., a reversal of the blood flow direction). For example, the MO.MA cerebral protection device developed by Invatec (Italy) operates on this principal. In the MO.MA system a catheter device includes two inflatable balloons, which serve to occlude the suitable vessels and generate a reverse blood flow. In this design, the main catheter is essentially a balloon catheter having two inflation lumens that communicate with the two inflatable balloons. A working lumen is provided in the catheter where an external instrument can be guided to treat the stenosis.
Another system developed by W.L. Gore & Associates, Inc. (GORE Neuro Protection System) utilizes a catheter having an inner lumen along with a distally located inflatable balloon sheath. A separate balloon wire is guided within the inner lumen of the catheter. The balloon wire is advanced into the external carotid artery (if the stenosis is present in the internal carotid artery) and the balloon is expanded to occlude the external carotid artery. Antegrade blood flow in the direction of the external carotid artery will thereby be stopped. The second inflatable balloon sheath, which is positioned at the distal end of the balloon catheter, is then inflated to occlude the common carotid artery. The blood flow of the common carotid artery will thus be stopped. Flow reversal is achieved at the treatment site by selective occlusion of the external carotid artery and the common carotid artery. Blood that tries to flow from the internal carotid artery to the common carotid artery will be hindered by the balloon sheath of the balloon catheter and instead is guided into the lumen of the balloon catheter for filtration and subsequent redirection into the patient via venous return. A working device such as a dilation balloon catheter, which is necessary for the further dilation of the stenosis, is guided within the balloon catheter lumen.
By inducing retrograde blood flow, the above-mentioned systems can potentially avoid a migration of particles in the direction of the cerebral blood vessels. Also, a penetration of the area of the stenosis is not necessary. The above-noted systems are, however, disadvantageous because they require relatively large dimensions. In particular, the inner diameter of the balloon catheter has to be large due to the various system components to be guided therein (e.g., external balloon and other intervention tools). In addition, the incorporation of the inflation lumen(s) into the catheter makes for devices having larger diameters and reduced space available for the working lumen. This is a particular concern because the sizes of the therapeutic and diagnostic tools for carotid artery intervention are constrained due to the limited space available within the balloon catheter. It may not be possible to adapt the size of the intervention tools to the required small size.
There thus is a need for improved methods and devices for occluding one or move vessels to protect cerebral vessels and the brain. For instance, there is a need to have occlusion devices that have a relatively low profile (e.g., outer diameter). Smaller devices are more manageable to handle at the vascular access site (e.g., femoral artery) and offer additional flexibility through the tortuous vascular anatomy. There is a need for an occlusion device that is easier to use than the devices described above. For example, the GORE Neuro Protection System uses separate elongate devices having inflatable balloons thereon. A single device that incorporates both proximal and distal occlusive elements is easier to use. In addition, an occlusion device should be able to be used with a single guidewire that can be used for protection device deployment as well as delivery of a working instrument such as a stent or balloon catheter.
Additionally, there is a need for a device that incorporates a single step to deploy the proximal and distal occlusion elements. For example, in the MO.MA cerebral protection device, two separate inflation lumens (one for proximal balloon and one for distal balloon) must be actuated for full deployment of the occlusive balloons. For full deployment of the balloons in the GORE Neuro Protection device, as explained above, the user must inflate the balloon wire in addition to the separate balloon sheath located on the distal end of the catheter. In addition, it would be preferably to provide a device having occlusive elements that do not need the cumbersome and space-occupying inflation lumens used in balloon-based devices. The device should also have the ability to rapidly re-establish normal or antegrade flow given the potential for occlusion intolerance in the patient. Finally, the device should offer near constant procedural imaging capability.